General provisions for expansion agents

① In concrete projects, calcium sulfoaluminate, calcium oxide, magnesium oxide, and metal expansion agents can be used.

② Expansion agent can be used to compensate for shrinkage concrete (mortar), fill with expansion agent concrete (mortar), and self-stressing concrete (mortar).

③ Concrete (mortar) prepared with calcium sulfoaluminate expansion agent shall not be used in projects where the ambient temperature is above 80°C for a long time.

④ Filling expansion mortar mixed with iron filing expansion agent shall not be used in projects with stray current and in parts in contact with aluminum-magnesium materials.

⑤ The shrinkage-compensating concrete (mortar) should meet the relevant regulations of JC476-98. The performance of self-stressed expansion concrete should comply with the regulations of (JG218-79 and JG219-79).

⑥ For calcium sulfoaluminate expansion agent (except alunite) and calcium oxide expansion agent, Portland cement or ordinary Portland cement should be used. Other cements should be determined by testing. The alunite expansion agent should be ordinary Portland cement or slag Portland cement. If other cements are used, they should be determined through tests.

⑦ The mix ratio equipment of expansion agent concrete is the same as that of ordinary concrete, and the amount of expansion agent should be calculated according to the internal mixing method. The cement grade should not be less than 32.5Mpa, and the minimum cement dosage should not be less than 300kg/m3. The self-stressing concrete shall not be less than 500kg/m3.

⑧ The variety and dosage of expansion agent should be selected based on the nature of the project and construction conditions, and the mix ratio should be determined through preparation tests. The allowable amount of concrete containing expansion agent The transportation and pouring time should be determined based on tests.

⑨ For concrete mixed with calcium sulfoaluminate or calcium oxide, chlorine salt admixtures should not be used.

⑩ Expansive concrete should be stirred mechanically, and it must be stirred evenly. The stirring time should be no less than 3 minutes, and should be 30 seconds longer than concrete without additives.

⑾ The shrinkage-compensating concrete (mortar) should be mechanically vibrated and must be dense. Mechanical vibration shall not be used for filling expanded concrete with a slump of more than 150 mm, or expanded mortar with a jumping table flow rate of more than 250 mm. In parts such as the base of pouring machinery and equipment that are not suitable for air removal, flexible materials such as bamboo strips can be inserted and tamped. Each pouring part must be poured from one direction.

⑿ Expansive concrete (mortar) must be cured in a humid state for less than 14 days or cured with spray curing agent. When the daily minimum temperature is below 5℃, moisturizing measures should be taken. Expansive concrete (mortar) can be cured with steam below 80°C. The curing system should be determined through experiments based on the types of expansion agents and cement types. </p